After reading through the many forum entries on teslamotorsclub.com where most of the solutions are based on installing rather complicated (at least for me) LED strips by using already existing wires, I found a much easier solution which can be done in 5 minutes.

I ordered these LED strips on amazon. They are self powered using 4 AAA batteries and have a motion sensor built in that only activates in low light conditions.

One of the LED lights after installation. They automatically turn off after 15 seconds if no motion is detected. They are supposed to last thousands of hours.

The unit detached from the magnetic strip. Makes it very easy to change batteries if necessary

The product image from Amazon

They come with a magnetic strip that fits perfectly underneath the trunk cover. I placed them on the left and right sides right underneath the plastic supports that hold the trunk cover. It's a perfect fit.

So you just insert the batteries, attach the magnetic strip and voilà - instant trunk lighting without all the hassle of finding the right wires and possibly messing something up : )